From: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Subject: ocfs2: fix snprintf() checking The snprintf() function returns the number of bytes which would have been printed if the buffer was large enough. In other words it can return ">= remain" but this code assumes it returns "== remain". The run time impact of this bug is not very severe. The next iteration through the loop would trigger a WARN() when we pass a negative limit to snprintf(). We would then return success instead of -E2BIG. The kernel implementation of snprintf() will never return negatives so there is no need to check and I have deleted that dead code. Link: https://lkml.kernel.org/r/20210511135350.GV1955@kadam Fixes: a860f6eb4c6a ("ocfs2: sysfile interfaces for online file check") Fixes: 74ae4e104dfc ("ocfs2: Create stack glue sysfs files.") Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> Cc: Mark Fasheh <mark@xxxxxxxxxx> Cc: Joel Becker <jlbec@xxxxxxxxxxxx> Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx> Cc: Changwei Ge <gechangwei@xxxxxxx> Cc: Gang He <ghe@xxxxxxxx> Cc: Jun Piao <piaojun@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/ocfs2/filecheck.c | 6 +----- fs/ocfs2/stackglue.c | 8 ++------ 2 files changed, 3 insertions(+), 11 deletions(-) --- a/fs/ocfs2/filecheck.c~ocfs2-fix-snprintf-checking +++ a/fs/ocfs2/filecheck.c @@ -326,11 +326,7 @@ static ssize_t ocfs2_filecheck_attr_show ret = snprintf(buf + total, remain, "%lu\t\t%u\t%s\n", p->fe_ino, p->fe_done, ocfs2_filecheck_error(p->fe_status)); - if (ret < 0) { - total = ret; - break; - } - if (ret == remain) { + if (ret >= remain) { /* snprintf() didn't fit */ total = -E2BIG; break; --- a/fs/ocfs2/stackglue.c~ocfs2-fix-snprintf-checking +++ a/fs/ocfs2/stackglue.c @@ -500,11 +500,7 @@ static ssize_t ocfs2_loaded_cluster_plug list_for_each_entry(p, &ocfs2_stack_list, sp_list) { ret = snprintf(buf, remain, "%s\n", p->sp_name); - if (ret < 0) { - total = ret; - break; - } - if (ret == remain) { + if (ret >= remain) { /* snprintf() didn't fit */ total = -E2BIG; break; @@ -531,7 +527,7 @@ static ssize_t ocfs2_active_cluster_plug if (active_stack) { ret = snprintf(buf, PAGE_SIZE, "%s\n", active_stack->sp_name); - if (ret == PAGE_SIZE) + if (ret >= PAGE_SIZE) ret = -E2BIG; } spin_unlock(&ocfs2_stack_lock); _
